The present invention relates to an improved swing prism arrangement for varying the direction of view in a borescope or endoscope.
Borescopes and endoscopes are well known devices for viewing features at remote or inaccessible locations, such as within complex machinery or within the human body. Many such devices are provided with a rotatable prism (a so-called xe2x80x9cswing prismxe2x80x9d) at the distal end of the device to provide a continuously variable direction of view. Typically, the maximum range of variation in direction of view which can be obtained is in the region of 70xc2x0 and it is usually necessary to provide different scopes for forward and lateral viewing.
The present invention provides apparatus for use as a borescope or endoscope, comprising a tube having a proximal end and a distal end; a viewing port at the distal end; means in the tube for receiving a image of a viewed field through the viewing port for transmission to a viewing device, the image receiving means defining a longitudinal axis; a first reflector having a reflective surface mounted at 45xc2x0 to the longitudinal axis and laterally offset therefrom, and mounted for rotation about a rotation axis perpendicular to and intersecting the longitudinal axis and intersecting the centre of the reflective surface; a second reflector having a reflective surface mounted at 45xc2x0 to the longitudinal axis and intersected by the longitudinal axis, such that light entering the viewing port is reflected by the first reflector to the second reflector and by the second reflector into the image receiving means; and further comprising means to illuminate the viewed field, comprising means to transmit light to a third reflector in the distal end of the tube and having a reflective surface mounted symmetrically about the longitudinal axis with respect to the first reflector and rotatable synchronously with the first reflector about the rotation axis.
The means for receiving an image may comprise a plurality of lenses for transferring the image from the distal to the proximal end of the tube. In this case, the viewing device may comprise an eyepiece assembly at the proximal end of the tube.
Alternatively, the means for receiving the image may comprise an image-to-video conversion device. In this case, the viewing device may comprise a screen for displaying a video image.
The means to transmit light conveniently comprises a bundle of optical fibres and at least one light guide and/or at least one right-angle prism.
In one embodiment, the means to transmit light includes three right-angled prisms.
The means to transmit light may include a right-angle prism mounted such that its hypotenuse face is adjacent the back of the first reflective surface.
In the apparatus, one or more of the first, second and third reflectors typically comprise a right-angle prism.
The apparatus may further comprise means to prevent rotation of the viewed image as the first reflector rotates about the rotation axis.
When the image receiving means comprises an image-to-video conversion device, it may be mounted to rotate synchronously with the first reflector to prevent rotation of the viewed image.
Alternatively, the means to prevent rotation of the viewed image may comprise a dove prism, a double dove prism or a Pechan prism.
In this case, the apparatus preferably also comprises means to correct inversion of the image produced by the rotation preventing prism(s).
The means to correct inversion of the image may also comprise a dove prism, a double dove prism or a Pechan prism.
The invention also provides apparatus for use a borescope or endoscope, comprising a tube having proximal and distal ends, a viewing port at the distal end, means to gather an image of a viewed field through the viewing port for transmission to a viewing device and means to illuminate the viewed field, comprising a plurality of optical fibres for transmitting light through the tube to the distal end, a reflector operable to reflect light from the fibres out of the tube, and means to transmit light from the fibres to the reflector comprising at least one light guide and/or at least one right-angled prism.
Preferably, the reflector is rotatably mounted and may comprise a right-angled prism.
Preferably, each light guide and/or right-angled prism in the means to transmit light is spaced from each adjacent light guide or prism by a spacing greater than approximately 1 wavelength.